Classification of Proteins

Classification of Proteins MDCAT MCQs with answers

13 past paper MCQs on Classification of Proteins, from the Macromolecules unit of MDCAT Chemistry. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.

Read the notes first Practise the unit as a quiz

1.Which one of the following is not an amino acid? (MDCAT 2024)

  1. lactic acid
  2. glutamic acid
  3. glycine
  4. lysine
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Correct answer: (a) lactic acid

Lactic acid carries a hydroxyl group where an amino acid carries an amino group.

2.The most abundant protein in animal kingdom forming 25–35% of body proteins is/are: (NUMS MDCAT 2025)

  1. Derived proteins
  2. Simple proteins
  3. Compound proteins
  4. Conjugated proteins
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Correct answer: (b) Simple proteins

Simple proteins yield only amino acids on hydrolysis, and they are the commonest kind in animals.

3.Which one of the following is not an amino acid (UHS MDCAT 2024)

  1. Folic acid
  2. Glutamic acid
  3. Glycine
  4. Lysine
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Correct answer: (a) Folic acid

Folic acid is a vitamin; the other three are amino acids.

4.Which of the following is produced by heating of bones? (PMC Practice 2021)

  1. Gelatine
  2. Cheese
  3. Albumin
  4. Gelly
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Correct answer: (a) Gelatine

Boiling bones breaks the collagen down to gelatine.

5.Based on the physico-chemical properties, proteins may be classified into the following types: (PMC MDCAT 2020)

  1. Simple proteins
  2. Compound proteins
  3. Derived proteins
  4. All of the above
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Correct answer: (d) All of the above

Proteins are classed as simple, compound or derived.

6.Amino acids are bi-functional compounds, with a general formula NH2CH(R)CO2H. A tripeptide is formed between Alanine (ala), Glycine (gly), and lysine (lys). There is no repetition of amino acid in this tri-peptide; Suggest how many tri-peptides are possible? (UHS MDCAT 2019)

  1. 9
  2. 6
  3. 3
  4. 12
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Correct answer: (b) 6

Three different residues can be arranged in $3!$ orders, that is six.

7.Which of the following bond is responsible for joining the amino acids in proteins? (UHS MDCAT 2019)

  1. Peptide Bond
  2. Ionic Bond
  3. Metallic Bond
  4. Disulfide Bond
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Correct answer: (a) Peptide Bond

Amino acids are joined by peptide bonds.

8.Amino acids react with each other such that -COOH group of one amino acid reacts with the -NH2 group of another amino acid to give a condensed structure as shown below: (UHS MDCAT 2018)

  1. Ester linkage
  2. Peptide linkage
  3. Carbide linkage
  4. Azide linkage
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Correct answer: (b) Peptide linkage

The link between two amino acids is the peptide bond.

9.The stability in the following structure is due to the: (UHS MDCAT 2018)

  1. Weak van der Waal’s forces
  2. Disulfide bridges
  3. Presence of unpaired electron in the structure
  4. Hydrogen bonding between NH group of one peptide and CO group of another peptide
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Correct answer: (d) Hydrogen bonding between NH group of one peptide and CO group of another peptide

The helix is held by hydrogen bonds between the NH of one peptide group and the CO of another.

10.Phosphoprotein comes under the type of which proteins: (UHS MDCAT 2017)

  1. Simple protein
  2. Conjugated protein
  3. Derived protein
  4. Both Conjugated & Derived protein
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Correct answer: (b) Conjugated protein

A phosphoprotein is a protein with a non-protein group attached, so it is conjugated.

11.When acid is added to an amino acid, which one of the following will act as a base? (UHS MDCAT 2016)

  1. NH3+
  2. COO-
  3. H+
  4. R group
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Correct answer: (b) COO-

The carboxylate group of the zwitterion takes the added proton.

12.Which one of the following is simplest amino acid? (UHS MDCAT 2016)

  1. Lysine
  2. Leucine
  3. Alanine
  4. Glycine
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Correct answer: (d) Glycine

Glycine has a single hydrogen atom for its side chain.

13.In the formation of Zwitter ion which one of the following donates the proton? (UHS MDCAT 2016)

  1. COOH
  2. NH2
  3. CH2COO-
  4. OH-
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Correct answer: (a) COOH

The carboxyl group gives its proton to the amino group, and the ion carries both charges.

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